Question:
I keep seeing references to the superiority or coaxial digital interconnects versus optical ones, but no one says either why or what the audible difference is. So my question is, why are they better, and what is the audible difference? After all, they are just sending a bunch of zeros and ones from one place to another, what makes one better?

Answer:
Each cable does indeed carry the same signal, a simple stream of ones and zeroes - seems like that should be easy. In theory the different types of digital cables (coaxial, TOSLINK optical, and others) should not have any audible differences. However, in theory rarely translates to in fact, which is the case with these cable types.

The task of sending ones and zeroes through the wire is fairly simple. A coaxial cable sends an electric signal with its voltage or lack there of representing the digital bits. An optical cable (TOSLINK as used by most people) sends pulses of light to represent the same bits. The optical TOSLINK cable uses thin, clear plastic fibers to transmit the pulses of light. The problem with this design is that the light tends to bounce around inside the cable, especially when the cable is turned in fairly tight curves or extends long distances. As the light bounces around, it throws off the timing of the signal. A digital signal''s series of ones and zeroes should arrive in a very exact time frame. When the bits do not arrive at quite the right time we encounter jitter. Jitter is simply a timing error, but this timing error can create audible distortion. So transmitting the bits is not the only job of a cable, minimizing (or not introducing) jitter is another important task.

Coaxial cables are subject to jitter problems, it is not an issue for TOSLINK cables only, however, coax cables tend to suffer from less jitter problems. Thus is the signal is the same but the coaxial cable introduces less distortion in the form of jitter timing errors the coax connection can produce a more perfect signal. Is there a difference? Yes. Is it audible? It can be. Should you be concerned? Not overly. If you have the option between coaxial and TOSLINK digital connections, go the coaxial route. If you have no option, the differences are subtle and TOSLINK works fine as a transmission format for digital bits.